
Here, the indicator \(b^e_{ij}\)  is multiplied to enforce the voltage drop relation only for the energized lines. Bilinear terms like \(b^e_{ij}v_i\)  in (REF ) can be handled by McCormick linearization, where the product terms are replaced by their linear convex envelopes to yield a relaxation of the original non-convex feasible set [1]}. If at most one of the variables is continuous and the rest are binary, this relaxation is exact. For illustration, let us consider a term \(z=xy\) , where \(x\)  is binary and \(y\)  is a continuous variable bounded in \(y\in [\underline{y},\overline{y}]\) . Here, \(z=xy\)  may be equivalently expressed as four linear inequality constraints.
\(x\underline{y}&\le z\le x\overline{y}\\y+(x-1)\overline{y}&\le z\le y + (x-1)\underline{y}\) 
